{
  "title": "What is collected determines which future attack is being discussed",
  "article": "https://synxcrypto.com/harvest-now-decrypt-later-bitcoin-ethereum#comparison-table",
  "reviewed": "2026-09-21",
  "scope": "Editorial reference table; not a SYNX laboratory measurement. Preserve qualifiers in each row.",
  "columns": [
    "Object available to an observer",
    "What is already visible?",
    "Potential future attack",
    "Relevant protection to inspect"
  ],
  "rows": [
    [
      "Ordinary Bitcoin public-ledger records",
      "Published transaction and script data",
      "No decryption is needed to read public records.",
      "Signature authorization and public-key exposure remain separate checks."
    ],
    [
      "Ordinary Ethereum public-ledger records",
      "Published transactions, state and contract data",
      "No decryption is needed to read public records.",
      "Account and validator authorization must be evaluated by their actual rules."
    ],
    [
      "Captured encrypted messages or service traffic",
      "Ciphertext and any recorded protocol exchange",
      "HNDL: later recovery of confidential plaintext, if the scheme becomes breakable.",
      "Key establishment, encryption, endpoint security and required secrecy lifetime."
    ],
    [
      "Exposed Bitcoin or Ethereum signing public keys",
      "Public verification material",
      "Future key recovery and forged authorization, given sufficient capabilities.",
      "Signature scheme, key exposure, accepted rules and migration status."
    ]
  ],
  "sources": [
    {
      "url": "https://www.nist.gov/cybersecurity-and-privacy/what-post-quantum-cryptography",
      "label": "NIST: HNDL concerns captured encrypted data"
    },
    {
      "url": "https://csrc.nist.gov/pubs/fips/203/final",
      "label": "NIST FIPS 203: key encapsulation and shared secrets"
    },
    {
      "url": "https://csrc.nist.gov/pubs/fips/204/final",
      "label": "NIST FIPS 204: the digital-signature function"
    },
    {
      "url": "https://synxcrypto.com/articles/02-when-will-quantum-computers-break-bitcoin-ecdsa.php",
      "label": "Existing Bitcoin article: public-key exposure and signature risk"
    },
    {
      "url": "https://synxcrypto.com/is-ethereum-quantum-safe-2026.php",
      "label": "Existing Ethereum page: public ledger and signature inventory only"
    },
    {
      "url": "https://synxcrypto.com/whitepaper.php",
      "label": "SYNX whitepaper: project-specified signature and key-encapsulation roles"
    }
  ]
}